Non-volatile memory, such as electrically erasable programmable read only memory (EEPROM) or flash memory, typically includes an arrangement of floating gate field effect transistors (FG-FET). The FG-FET includes a floating gate which is electrically isolated, creating a floating node, but which is capacitively connected to the channel of the field effect transistor. The FG-FET further has a control gate in a stacked arrangement with the floating gate. The control gate is positioned above the floating gate and is electrically isolated from the floating gate, but in capacitive contact with the floating gate. The charge in the floating gate, and hence the voltage thereof can be controlled by means of the control gate.
The arrangement of FG-FET is typically manufactured by providing a polycrystalline or amorphous dielectric layer on a crystalline substrate and depositing a floating gate layer of polycrystalline silicon on the dielectric layer. On the floating gate layer a control gate layer is deposited after a second dielectric layer is deposited, which separates the floating gate layer and the control gate layer. Typically, in conventional technology a dielectric layer of SiO2 or a tri-layer of SiO2/Si3N4/SiO2 (so called oxide-nitride-oxide or ONO layer) is deposited in order to obtain a high quality dielectric between the floating and the control gate.
However, a disadvantage of this process is that the characteristics of the floating gate layer, the second dielectric layer and the control gate layer cannot be controlled as accurately as would be desirable because they are deposited on a polycrystalline or amorphous layer. For example, the deposited dielectric layers have a relatively high density of defects and charge carrier traps both in the bulk of the dielectric material and at the interfaces. These defective sites might capture electrons, holes or even ionic contaminants that would distort the operation of the memory cell or make the distinction in reading between stored values very difficult if not impossible. Also,